Fixes #4890

Extension: Add HexFloatLiterals

Adds `virtual-modules` to handle cases like `GHC.Prim` from `ghc-prim`.

GHC's `ghc-prim` package has an `exposed-module` for which there exists no source code. As such it can't be built and has no interface file.  With the goal of getting rid of hacks in GHC `ghc-prim`s cabal file, which does the following:

```
flag include-ghc-prim
    Description: Include GHC.Prim in exposed-modules
    default: False
[...]
    if flag(include-ghc-prim)
        exposed-modules: GHC.Prim
```

and has this explaination in the build system:

```
# ----------------------------------------
# Special magic for the ghc-prim package

# We want the ghc-prim package to include the GHC.Prim module when it
# is registered, but not when it is built, because GHC.Prim is not a
# real source module, it is built-in to GHC.  The old build system did
# this using Setup.hs, but we can't do that here, so we have a flag to
# enable GHC.Prim in the .cabal file (so that the ghc-prim package
# remains compatible with the old build system for the time being).
# GHC.Prim module in the ghc-prim package with a flag:
#
libraries/ghc-prim_CONFIGURE_OPTS += --flag=include-ghc-prim

# And then we strip it out again before building the package:
define libraries/ghc-prim_PACKAGE_MAGIC
libraries/ghc-prim_dist-install_MODULES := $$(filter-out GHC.Prim,$$(libraries/ghc-prim_dist-install_MODULES))
endef
```

The addition of the `virtual-modules` has thus the effect of a module that is assumed to exist
but not tried to be built or listed in any of the module files.  It is however part of the
`exposed-modules` when registered into the package database

Disable tests and benchs by default on new-install

[ci skip]

And error if they are explicitly enabled, so we never try to install
remote packages with tests and/or benchs.

Fixes #4855

[ci skip]

Look for install includes in buildpref as well

When installing a lirbary, we should look for it's headers in it's 'build' preference first, then relative to the current path.

Initialize globalCacheDir in baseSavedConfig

This reverts commit bdb51a36.

Herbert Valerio Riedel authored 7 years ago and Mikhail Glushenkov committed 7 years ago

(cherry picked from commit 0a28ab6a)

Version range refactor

Add s/cmm-sources + extra-bundled-libraries

Apply 'any' qualifier to new-freeze constraints (fixes #4832).

Adds defaultMainWithHooksNoReadArgs

'makeAbsolute' is not compatible with old versions of 'directory' and
we know at this place in the code that the directory we refer to does
exist, so the potential exception is not a problem.

Fixes #4606.

(cherry picked from commit 560903cf)

Not absolutely happy with this solution. I fail to come up with a better one though.
The issue is that for some libraries, you might want to have _debug, _p, _l, as well as _thr_debug, _thr_p, _thr_l flavours.

# Conflicts:
#	Cabal/Distribution/PackageDescription/Parsec/FieldDescr.hs

# Conflicts:
#	Cabal/Distribution/PackageDescription/Check.hs
#	Cabal/Distribution/PackageDescription/Parsec/FieldDescr.hs
#	Cabal/Distribution/Parsec/Types/FieldDescr.hs
#	Cabal/doc/developing-packages.rst

new-install: nonlocal exes

[ci skip]

RFC: Relax coding guideline regarding module imports